#define _CRT_SECURE_NO_WARNINGS 1
#include <stdio.h>
 int my_strlen(char* a)
{
	int count = 0;
	if( *a=='\0')
		return 0;
	else
		count= my_strlen(a+1)+1;
	return count;
}
void exc(char* a)
{
	int right, t, left;
	for (t=0,left=0, right = my_strlen(a) - 1; left<=right; left++,right--)
	{
		t = a[left];
		a[left] = a[right];
		a[right] = t;
	}
}
int main()
{
	char arr[] = "abcdef";
	exc(arr);
	printf("%s\n", arr);
	return 0;
}